docs: def is_point(nc, variable):
      '''
      Returns true if the variable is a point feature type
  
      :param netCDF4.Dataset nc: An open netCDF dataset
      :param str variable: name of the variable to check
      '''
      # x(o), y(o), z(o), t(o)
      # X(o)
  
      dims = nc.variables[variable].dimensions
  
      cmatrix = coordinate_dimension_matrix(nc)
      first_coord = None
      if 't' in cmatrix:
          first_coord = cmatrix['t']
          if len(cmatrix['t']) > 1:
              return False
      if 'x' in cmatrix:
          if first_coord is None:
              first_coord = cmatrix['x']
          if first_coord != cmatrix['x']:
              return False
          if len(cmatrix['x']) > 1:
              return False
      if 'y' in cmatrix:
          if first_coord is None:
              first_coord = cmatrix['y']
          if first_coord != cmatrix['y']:
              return False
          if len(cmatrix['y']) > 1:
              return False
      if 'z' in cmatrix:
          if first_coord is None:
              first_coord = cmatrix['z']
          if first_coord != cmatrix['z']:
              return False
          if len(cmatrix['z']) > 1:
              return False
      if first_coord and dims != first_coord:
          return False
      # Point is indistinguishable from trajectories where the instance dimension
      # is implied (scalar)
      traj_ids = nc.get_variables_by_attributes(cf_role="trajectory_id")
      if traj_ids:
          return False
  
      return True